Azure CDN

Global content delivery network with POPs in 118+ cities, supporting Microsoft, Verizon, and Akamai backends, with dynamic site acceleration and WAF integration.

AzureIntermediate

Why

Azure CDN caches static and dynamic content at edge POPs, cutting latency for distant users and offloading origin traffic. The Standard Microsoft tier integrates with Azure Front Door WAF, custom domains, and compression, and bills by egress with no commit. Azure holds 21% cloud market share (Synergy Research Q4 2024).

Azure is the default for enterprises with Microsoft 365 / Active Directory estates — 95% of Fortune 500 use Azure. AKS and Cosmos DB are first-class for .NET workloads.

When

Use Azure CDN in front of Blob Storage, App Service, or any HTTP origin to accelerate global access. Choose Front Door (premium) when you need multi-region failover, URL rewriting, and WAF; use plain CDN for simple caching.

Avoid CDN for content that must never be cached (e.g., real-time dashboards) without careful cache-control headers.

How

1. Create a CDN profile (Standard Microsoft is cheapest and integrates with Front Door WAF). 2. Create an endpoint pointing at your origin (e.g., mystore.blob.core.windows.net). 3. Enable compression for text-based MIME types. 4. Add a custom domain and bind a TLS certificate (managed cert is free on Standard Microsoft). 5. Set caching rules: honor origin cache-control, or override with custom rules. 6. Optionally enable WAF with managed rule sets (OWASP). ```bash az cdn profile create --name mycdn --resource-group rg --sku Standard_Microsoft az cdn endpoint create --name myendpoint --profile-name mycdn --resource-group rg --origin mystore.blob.core.windows.net --origin-host-header mystore.blob.core.windows.net ```

Example

Purge the CDN cache after a new deployment so users see fresh content immediately: ```bash # purge everything az cdn endpoint purge --name myendpoint --profile-name mycdn --resource-group rg --content-paths "/*" # purge a specific path az cdn endpoint purge --name myendpoint --profile-name mycdn --resource-group rg --content-paths "/assets/app.js" ``` Origin serving proper cache headers so the CDN respects them: ```http HTTP/1.1 200 OK Cache-Control: public, max-age=86400 Content-Type: text/css ```

Common Problems

⚠Stale content after deploy — CDN caches per the cache-control header; either set shorter max-age or purge after deploy, and version asset filenames (app.abc123.js) for long max-age.
⚠Custom domain TLS shows 'pending' — DNS CNAME must propagate first; verify with nslookup, then Azure issues the managed cert automatically.
⚠Compression not working — ensure the origin returns Content-Encoding without compression and the CDN compression setting includes the MIME type (e.g., application/json).

Best Practices

✓Use content-addressed filenames (hash in filename) so you can set max-age=31536000 (1 year) and never serve stale content — no purge needed.
✓Put the CDN in front of Blob Storage with a custom domain to get clean URLs (cdn.example.com instead of mystore.blob.core.windows.net).
✓Enable WAF on Front Door/CDN Standard Microsoft with the OWASP 3.2 rule set to block SQLi/XSS at the edge before traffic reaches your origin.

FAQ

What is Azure CDN and what problem does it solve?

Global content delivery network with POPs in 118+ cities, supporting Microsoft, Verizon, and Akamai backends, with dynamic site acceleration and WAF integration. It lets developers deploy, store, and scale without self-managing infrastructure — a core reference for cloud service selection.

How do I get started with Azure CDN in 5 minutes?

Two steps to run it: (1) Create a CDN profile (Standard Microsoft is cheapest and integrates with Front Door WAF).; (2) Create an endpoint pointing at your origin (e.g., mystore.blob.core.windows.net).. Validate on the free tier first, then wire into production.

What is the #1 pitfall with Azure CDN?

The most frequent issue is: Stale content after deploy — CDN caches per the cache-control header; either set shorter max-age or purge after deploy, and version asset filenames (app.abc123.js) for long max-age.. Run a pre-launch checklist item by item, and add policy/config scanning in CI.

What are the best practices for Azure CDN?

Best practices for Azure CDN include: Use content-addressed filenames (hash in filename) so you can set max-age=31536000 (1 year) and never serve stale content — no purge needed.; Put the CDN in front of Blob Storage with a custom domain to get clean URLs (cdn.example.com instead of mystore.blob.core.windows.net).; Enable WAF on Front Door/CDN Standard Microsoft with the OWASP 3.2 rule set to block SQLi/XSS at the edge before traffic reaches your origin.. The first one — "Use content-addressed filenames (hash in filename) so you can set max-age=31536000 (1 year) and never serve stale content — no purge needed." — should be a team default baked into your IaC templates.

How do I control cost and avoid bill surprises with Azure CDN?

Three ways to prevent overspend: (1) tag every resource with env/team and enable billing alarms; (2) set budget thresholds to trigger Slack/email alerts; (3) review idle resources in Cost Explorer regularly and clean them up. Most Azure CDN options offer a free tier — validate within free quota before scaling.